Today's highly competitive economy has led to short product design cycles for bringing innovative and improved products to market, the widespread implementation of just-in-time inventory, and a demand for high quality/low cost products. To remain competitive in this environment, manufacturers need tools which can make the manufacturing process more efficient and less costly.
At present, considerable time and effort is required to take basic part defining data and develop a "process plan" for manufacturing the part, including generating high quality engineering drawings of the part, generating program code executable by device controllers for manufacturing the part, and generating a computer simulation of the manufacturing processes for producing the part that will assist in verifying and debugging the processes.
"Process planning" refers to the activities necessary to translate basic part defining data into manufacturing operation details. The activities of a process plan include analysis of the basic part defining data, selection of a raw workpiece, determining manufacturing processes (e.g., machining operations) and their sequences, selection of machine tools and their associated operating tools (e.g., drills, cutters, etc.) for carrying out the processes on the workpiece, selection of work holding devices, selection of inspection equipment, and determining machining conditions (e.g., cutting speeds and feeds and depth of cut) and manufacturing times (e.g., set-up time, processing time, and lead time). It should be appreciated that the basic part defining data is defined to include geometric part features, dimensional data and tolerance specifications.
When developing a manufacturing plan for producing a part, the basic part defining data is analyzed by first performing an analysis of the geometric part features. Typical part features are planes, cylinders, cones, steps, edges and fillets. These common part features may be modified by the addition of detail elements such as grooves, key ways, threads, slots, pockets and holes, among others. Following part feature analysis, dimensional and tolerance analysis are performed to provide additional information for manufacturing purposes.
The manufacturing plan further requires selection of the raw workpiece, which involves defining such characteristics as shape, size (i.e., dimensions and weight) and material type. For instance, a raw workpiece may be in the shape of a rod, a slab or merely a rough forging. The dimensions, weight and the material type of the raw workpiece will be dictated by the physical and functional characteristics of the part to be manufactured.
Defining the manufacturing plan also involves determining the manufacturing processes (e.g., machining operations) and their sequences to transform the raw workpiece to a finished part having the desired part features, dimensions and tolerances. In many cases, there will be several ways to produce a part with a given design, and many factors, including the basic part defining data, influence the selection and sequence of the various manufacturing processes. For instance, a part requiring a hole with low tolerance and surface roughness specifications will require a simple drilling operation. In contrast, the same part with much finer surface finish and closer tolerance requirements will require first a drilling operation and then a boring operation to obtain the desired surface roughness and the tolerance on the hole feature of the part. Moreover, in some cases, manufacturing processes are dependent upon one another. In this respect, the holes may be required to be drilled before milling the inclined surface because the holes cannot be drilled accurately on an inclined surface. However, if the inclined surface has to be finished before drilling, an end mill will be needed to obtain a flat surface perpendicular to the axis of the drill before drilling the hole.
Machine tools also must be selected as part of defining a manufacturing plan. In selecting a machine tool, workpiece-related attributes, machine tool-related attributes and production volume must be considered. Workpiece-related attributes relate to the kinds of part features desired, the dimensions of the workpiece, its dimensional tolerance and the raw material form. Machine tool-related attributes relate to the process capability, mode of operation (e.g., manual, semi-automatic, automatic, numerically controlled), tooling capabilities (e.g., size and type of tool magazine) and automatic tool changing capabilities. Production volume-related information is directed to items such as the production quantity and purchase order frequency. Further the type and size of operating tool required to perform the various machining operations to generate each of the part features on the workpiece also must be determined.
Machining conditions associated with each machining operation and manufacturing times are determined to reduce costs and increase the production rate and also must be included in the manufacturing plan. A number of mathematical models for ascertaining the optimal machining conditions are known, including those directed to minimum cost per piece, maximum production rate models and manufacturing lead times.
A manufacturing plan must also specify work holding devices, such as clamps, jigs and fixtures, to locate and hold the workpiece. Finally, inspection equipment necessary to ensure the dimensional accuracy, tolerances and surface finish on the features also must be selected.
In addition to the complexities involved with process planning, complexities are also encountered in taking geometric part features, dimension data and tolerance specifications and generating high quality engineering drawings for a part and computer simulations of the manufacturing plan carried out to produce the part so that the manufacturing plan can be verified and debugged.
In view of the foregoing, there is a need to organize and process the data required to define a manufacturing plan for producing a part, to generate engineering drawings of the part, and to generate a computer simulation of the manufacturing plan. There is also a need to combine the foregoing functions into an integrated system so that data can be easily and efficiently transferred therebetween.